Many different technologies have been developed for fabricating switches and relays for low frequency and high frequency switching applications. Many of these technologies rely on solid, mechanical contacts that are alternatively actuated from one position to another to make and break electrical contact. Unfortunately, mechanical switches that rely on solid-solid contact are prone to wear and are subject to a condition referred to as “fretting.” Fretting refers to erosion that occurs at the points of contact on surfaces.
To minimize mechanical damage imparted to switch and relay contacts, switches and relays have been fabricated using liquid metals to wet the movable mechanical structures to prevent solid to solid contact. It is also possible to move a volume a liquid metal, creating a switch without any solid moving parts.
A liquid metal microswitch is described in U.S. Pat. No. 6,559,420, assigned to the assignee of the present application, and hereby incorporaed by reference. The liquid metal microswitch in U.S. Pat. No. 6,559,420 uses gas pressure to divide one of two liquid metal switching elements to provide the switching function. For a SPDT (single pole, double throw) switch, one of the two liquid metal elements is always in contact with the input electrode and with one output electrode, and one liquid metal element is always in contact with the other output electrode (the isolated output electrode, also referred to as the isolated port). The application of pressure to the liquid metal that connects the input electrode to one of the output electrodes will toggle the switch to the other state, providing SPDT action. Unfortunately, using two elements of liquid metal causes the microswitch to be susceptible to capacitive coupling into the isolated port. Further, dividing one of the liquid metal elements of the microswitch frequently causes fragmentation of the liquid metal element through the formation of one or more microdroplets, also referred to as “satellites.” Microdroplets frequently form when one of the liquid metal elements is divided by the gas pressure. The microdroplets may enter the gas conduit through which actuating pressure is directed, clogging the conduit channel and reducing the amount of liquid metal available for switching.